c
c petersen graph
c has no solution because of sup>2 => one must be green condition
c
p edge 10 15
e 1 2
e 2 3
e 3 4
e 4 5
e 5 1
e 1 6
e 2 7
e 3 8
e 4 9
e 5 10
e 6 7
e 7 8
e 8 9
e 9 10
e 10 6

